5 Answers
5

You will have to make some adjustments, but don't let that stop you. Remember famous percussionist Evelyn Glennie is deaf.

Check out this one armed bass player. He plays all notes by hammering-on or pulling-off with his left hand. The only modification to his instrument is a handkerchief round the nut to damp the open strings.

It sure will influence your piano playing. Every part of anatomy does. What this most likely will result in is that you have to take fingerings in a score (in particular standard scale exercises) with more of a grain of salt than most others, and that there will be the occasional stuff that will be hard to play unchanged.

The range of affected music would still be less than if you, say, chose to play accordion instead (which does not really make use of the left thumb). If you want to get closer to playing typical piano music with that kind of instrument, you probably want to take a converter instrument (allowing for the left hand to be playing single notes) and it makes sense learning chromatic button accordion since then you are able to play with more consistent voicings (passing a voice between left and right hand as it is often done on the piano is not possible on an accordion without audible change of character). Also, the total accessible range in the right hand for a concert-style largest-size button accordion is 64 notes, while it is 45 for a piano accordion. And for misappropriating piano music, range is an issue.

At any rate, the mobility of fingers can be changed quite a bit with training. If your thumb is restricted as described, one may suspect that even within its accessible range of motion, it might have restricted dexterity. So it's basically your own judgment call whether you think the total of your thumb to be problematic to a degree where you prefer to use an instrument that either does not use the thumb, or uses it in a very limited fashion (wind instruments tend not to require moving thumbs as much as opening and closing them mostly in-place, or even just using them for holding the instrument).

My left thumb is kept relatively straight at most times so the 1st joint from the tip is barely utilised.

The position where the left thumb needs to be largely dictates the position of the rest of my hand.

When my left thumb presses a key, it seems to make its up-down action with the palm relatively still, using the hidden joint at the base of the wrist, 3rd in from the tip of the thumb, rather than the joint 2nd in from the tip, which I think is the joint you're asking about.